Semiconductor processing equipment having improved process drift control

ABSTRACT

A plasma processing chamber including a slip cast part having a surface thereof exposed to the interior space of the chamber. The slip cast part includes free silicon contained therein and a protective layer on the surface which protects the silicon from being attacked by plasma in the interior space of the chamber. The slip cast part can be made of slip cast silicon carbide coated with CVD silicon carbide. The slip cast part can comprise one or more parts of the chamber such as a wafer passage insert, a monolithic or tiled liner, a plasma screen, a showerhead, dielectric member, or the like. The slip cast part reduces particle contamination and reduces process drift in plasma processes such as plasma etching of dielectric materials such as silicon oxide.

This application is a divisional of application Ser. No. 09/469,300,filed on Dec. 22, 1999 now U.S. Pat. No. 6,673,198, which isincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to semiconductor processing equipment and moreparticularly to improved process drift control during processing such asplasma etching of semiconductor substrates.

BACKGROUND OF THE INVENTION

In the field of semiconductor processing, vacuum processing chambers aregenerally used for etching and chemical vapor deposition (CVD) ofmaterials on substrates by supplying an etching or deposition gas to thevacuum chamber and application of an RF field to the gas to energize thegas into a plasma state. Examples of parallel plate, transformer coupledplasma (TCP™) which is also called inductively coupled plasma (ICP), andelectron-cyclotron resonance (ECR) reactors and components thereof aredisclosed in commonly owned U.S. Pat. Nos. 4,340,462; 4,948,458;5,200,232 and 5,820,723. Because of the corrosive nature of the plasmaenvironment in such reactors and the requirement for minimizing particleand/or heavy metal contamination, it is highly desirable for thecomponents of such equipment to exhibit high corrosion resistance.

During processing of semiconductor substrates, the substrates aretypically held in place within the vacuum chamber on substrate holdersby mechanical clamps and electrostatic clamps (ESC). Examples of suchclamping systems and components thereof can be found in commonly ownedU.S. Pat. Nos. 5,262,029 and 5,838,529. Process gas can be supplied tothe chamber in various ways such as by gas nozzles, gas rings, gasdistribution plates, etc. An example of a temperature controlled gasdistribution plate for an inductively coupled plasma reactor andcomponents thereof can be found in commonly owned U.S. Pat. No.5,863,376.

Aluminum and aluminum alloys are commonly used for walls of plasmareactors. In order to prevent corrosion of the walls, various techniqueshave been proposed for coating the aluminum surface with variouscoatings. For instance, U.S. Pat. No. 5,641,375 discloses that aluminumchamber walls have been anodized to reduce plasma erosion and wear ofthe walls. The '375 patent states that eventually the anodized layer issputtered or etched off and the chamber must be replaced. U.S. Pat. No.5,680,013 states that a technique for flame spraying Al₂O₃ on metalsurfaces of an etching chamber is disclosed in U.S. Pat. No. 4,491,496.The '013 patent states that the differences in thermal expansioncoefficients between aluminum and ceramic coatings such as aluminumoxide leads to cracking of the coatings due to thermal cycling andeventual failure of the coatings in corrosive environments. U.S. Pat.No. 5,085,727 discloses a carbon coating for walls of a plasma chamberwherein the coating is deposited by plasma assisted CVD.

In order to protect the chamber walls, U.S. Pat. Nos. 5,366,585;5,556,501; 5,788,799; 5,798,016; and 5,885,356 propose linerarrangements. For instance, the '585 patent discloses a free standingceramic liner having a thickness of at least 0.005 inches and machinedfrom solid alumina. The '585 patent also mentions use of ceramic layerswhich are deposited without consuming the underlying aluminum can beprovided by flame sprayed or plasma sprayed aluminum oxide. The '501patent discloses a process-compatible liner of polymer or quartz orceramic. The '799 patent discloses a temperature controlled ceramicliner having a resistance heater embedded therein and the ceramic can bealumina, silica, titania, zirconia, silicon carbide, titanium carbide,zirconium carbide, aluminum nitride, boron nitride, silicon nitride andtitanium nitride. The '016 patent discloses a liner of ceramics,aluminum, steel and/or quartz with aluminum being preferred for its easeof machinability and having a coating of aluminum oxide, Sc₂O₃ or Y₂O₃,with Al₂O₃ being preferred for coating aluminum to provide protection ofthe aluminum from plasma. The '356 patent discloses a ceramic liner ofalumina and a ceramic shield of aluminum nitride for the wafer pedestalfor use in CVD chambers.

U.S. Pat. No. 5,904,778 discloses a SiC CVD coating on free standing SiCfor use as a chamber wall, chamber roof, or collar around the wafer.U.S. Pat. No. 5,292,399 discloses a SiC ring surrounding a waferpedestal. A technique for preparing sintered SiC is disclosed in U.S.Pat. No. 5,182,059.

In addition to the above, the use of silicon carbide in semiconductorprocessing equipment is disclosed in U.S. Pat. Nos. 4,401,689 (susceptortube), 4,518,349 (furnace support rod), 4,999,228 (diffusion tube),5,074,456 (upper electrode), 5,252,892 (plasma cathode chamber),5,460,684 (resistive layer of ESC), 5,463,525 (sensing pin), 5,578,129(filter plate of load lock system), 5,538,230 (wafer boat), 5,595,627(upper electrode), 5,888,907 (electrode plate), and 5,892,236 (ionimplantation device).

Other documents include Japanese Patent Publication Nos. 60-200519(susceptor), 63-35452 (diffusion oven tube, liner tube, port element,paddle), 63-186874 (microwave heated sample plate), 63-138737 (upperelectrode of plasma etch reactor), 3-201322 (coating for part in vacuumenvironment), and 8-17745 (wafer heater). Of these, Japanese PatentPublication No. 63-35452 discloses parts made of slip cast siliconcarbide.

With regard to plasma reactor components such as showerhead gasdistribution systems, various proposals have been made with respect tothe materials of the showerheads. For instance, commonly owned U.S. Pat.No. 5,569,356 discloses a showerhead of silicon, graphite, or siliconcarbide. U.S. Pat. No. 5,888,907 discloses a showerhead electrode ofamorphous carbon, SiC or Al. U.S. Pat. Nos. 5,006,220 and 5,022,979disclose a showerhead electrode either made entirely of SiC or a base ofcarbon coated with SiC deposited by CVD to provide a surface layer ofhighly pure SiC.

In discussing the need for cleanliness and the elimination ofcontaminants in the processing of semiconductor wafers; U.S. Pat. No.5,538,230 references U.S. Pat. Nos. 3,962,391; 4,093,201; 4,203,940;4,761,134; 4,978,567; 4,987,016 and Japanese Publication No. 50-90184.The '230 patent also references U.S. Pat. Nos. 3,951,587 and 5,283,089for discussions of SiC parts and references U.S. Pat. No. 4,761,134 fora discussion of CVD SiC on Si infiltrated SiC or porous Si that has notbeen filled with Si.

Japanese Publication No. 63-273323 discloses SiC parts for an ECR plasmadeposition apparatus wherein silicon dioxide is deposited on samples,the SiC parts being coated with SiC by generating a plasma in thechamber and introducing methane and silane gases into the chamber.

In view of the need for high purity and corrosion resistance forcomponents of semiconductor processing equipment, there is a need in theart for improvements in materials and/or coatings used for suchcomponents. Moreover, with regard to the chamber materials, anymaterials which can increase the service life of a plasma reactorchamber and thus reduce the down time of the apparatus, would bebeneficial in reducing the cost of processing the semiconductor wafers.

SUMMARY OF THE INVENTION

The invention provides a method of processing semiconductor substratesand reducing particle contamination and/or process drift duringconsecutive processing of the substrates. The method comprising steps of(a) placing a substrate on a substrate holder in an interior space of aplasma processing chamber, the processing chamber including at lease oneslip cast part having a surface exposed to the interior space, the slipcast part having free silicon contained therein and a protective layeron the surface which protects the silicon from being attacked by theplasma in the interior space, (b) processing the substrate by supplyingprocess gas to the processing chamber and energizing the process gasinto a plasma state in the processing chamber, the slip cast part beingexposed to the plasma and optionally providing a ground path for RFcurrent sustaining the plasma, (c) removing the substrate from theprocessing chamber, and (d) consecutively processing additionalsubstrates in the processing chamber by repeating steps (a-c) whileminimizing particle contamination of the substrates and/or reducingprocess drift during the processing step as a result of protecting thefree silicon from attack by the plasma.

According to one optional aspect of the method, the slip cast part cancomprise a liner within a sidewall of the processing chamber and theprocessing chamber can include a substantially planar antenna whichenergizes the process gas into the plasma state by supplying RF power tothe antenna. For plasma etching of oxide materials, the process gas cancomprise one or more hydrofluorocarbon gases. For oxide etching, theplasma preferably comprises a high density plasma which etches an oxidelayer on the substrates while an RF bias is applied to the substrates.

The slip cast part can comprise one or more parts of the chamber. Forinstance, the slip cast part can comprise a liner within a sidewall ofthe processing chamber, a gas distribution plate supplying the processgas to the processing chamber, a perforated baffle extending between thesubstrate holder and an inner wall of the processing chamber, a waferpassage insert, a focus ring surrounding the substrate, a tubular linerprotecting a process monitoring device, or the like. In a preferredembodiment, the slip cast part is a wafer passage insert fitted in anopening in a ceramic liner within a sidewall of the processing chamberwherein the liner is heated by a heater which maintains the liner at adesired temperature. The slip cast part can consist essentially ofsilicon impregnated slip cast SiC coated with CVD SiC.

In an exemplary process, a first slip cast part comprises a heated linerand a second slip cast part comprises a plasma screen arranged such thatthe liner surrounds the substrate holder and the plasma screen extendsbetween the liner and the substrate holder, the liner being heated to atemperature above room temperature during the processing step. Inanother process, the slip cast part comprises a gas distribution platehaving a resistivity high enough to pass RF energy therethrough, theprocess gas being energized by an antenna which couples RF energy intothe chamber through the gas distribution plate. A third slip cast partcan comprise a chamber liner having a resistivity below 200 Ω·cm,preferably below 50 Ω·cm, and more preferably below 10 Ω·cm.

The invention also provides a plasma processing system useful forprocessing semiconductor substrates comprising a plasma processingchamber having an interior space bounded by a chamber sidewall, asubstrate support on which a substrate is processed within the interiorspace arranged such that the chamber sidewall is spaced outwardly of aperiphery of the substrate support, a gas supply through which processgas can be supplied to the interior space during processing of thesubstrate, an energy source which can energize the process gas in theinterior space into a plasma state during processing of the substrate,and a slip cast part having a surface thereof exposed to the interiorspace, the slip cast part having free silicon contained therein and aprotective layer on the surface which protects the silicon from beingattacked by the plasma in the interior space. According to a preferredembodiment, the slip cast part is of porous silicon carbide backfilledwith silicon and the protective layer is a chemical vapor depositedlayer of silicon carbide. A preferred slip cast part is a wafer passageinsert of a plasma etch reactor wherein the gas supply supplies afluorocarbon and/or a fluorohydrocarbon to the interior space.

In a less preferred embodiment, the slip cast part is bonded to thechamber by an elastomer joint or the chamber can include a ceramic linerbetween the chamber sidewall and the substrate support wherein the slipcast part comprises a tubular liner in an opening extending through theliner. A preferred energy source is an antenna such as a planar coilwhich inductively couples radiofrequency energy through a dielectricmember into the chamber.

According to a preferred embodiment, the interior of the chamber isbounded by a showerhead having a silicon carbide surface extendingacross the top of the chamber, a liner having a silicon carbide surfaceextending downwardly from the silicon carbide surface of the showerhead,a plasma screen having a silicon carbide surface extending inwardly fromthe silicon carbide surface of the liner, and the slip cast partcomprises a wafer passage insert fitted in an opening in the liner, theCVD SiC coating forming a surface of the wafer passage insert throughwhich a semiconductor wafer passes into and out of the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a single wafer vacuum processing chamber having aninductively coupled plasma source and a tiled liner of slip cast partsin accordance with the invention;

FIG. 2 shows the plasma reaction chamber of FIG. 1 without variouscomponents including the tiled liner;

FIG. 3 shows details of a support arrangement for the tiled liner;

FIG. 4 shows a perspective view of the plasma chamber of FIG. 3;

FIG. 5 shows details of a slip cast wafer passage insert in accordancewith the invention;

FIG. 6 shows how edges of the tiles of FIG. 3 fit together in aninterlocking arrangement;

FIG. 7 shows a perspective view of a one piece slip cast wafer passageinsert in accordance with the invention;

FIG. 8 shows a top view of the insert shown in FIG. 7; and

FIG. 9 shows an enlarged view of a corner of the insert shown in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the invention, a plasma processing chamber having improvedprocess drift control is provided. The improved process drift control isachieved by use of one or more parts in the chamber of a part having asurface thereof exposed to the interior space, the part having freesilicon contained therein and a protective layer on the surface whichprotects the silicon from being attacked by the plasma in the interior.The free silicon can be silicon impregnated into a porous SiC body, thesilicon filling the porosity to minimize undesirable process effects andincrease electrical conductivity which is useful for lowering the RFimpedance of the part.

The part can have any desired configuration such as that of a waferpassage insert, a chamber wall, a substrate support, an electrode, ashowerhead, etc. According to a preferred embodiment, the part comprisesa slip cast silicon carbide part which has been backfilled orimpregnated with silicon and the protective coating preferably comprisesCVD silicon carbide.

The invention provides parts for a plasma chamber wherein the parts aremade entirely of Si and SiC. Such materials are compatible in plasmaenvironments since plasma erosion of Si or SiC produces gaseous Si or Ccompounds which can be pumped from the chamber without particlecontamination of the substrate. With regard to thermal control, SiC hasbeen found to exhibit exceptionally high thermal conductivity enablingparts of such material to be heated or cooled to a desired temperaturerange during processing of substrates such as silicon wafers.

Slip cast SiC parts in accordance with the invention can be made by thefollowing process. In the process, a bimodal distribution of SiC powderis prepared. For example, a first SiC fraction having a mean particlesize of 10 to 80 μm, preferably 25 to 50 μm is combined with a secondfraction having a mean particle size of 80 to 200 μm, preferably 100 to150 μm, the powder mixture is combined with water and organic agentssuch as a flocculent, and the mixture is poured into a mold to form aslip cast part. After drying such as at room temperature, the slip castpart is green machined and sintered at a suitable temperature such asaround 1500 to 2000° C., the sintered part is purified in an acid bath,the cleaned part is subjected to impregnation with silicon to fill theporosity (e.g., 15 to 20%) of the part such as by melting powderedsilicon and wicking the melted silicon through porous graphite and intothe part fill essentially 100% of the porosity in the part, cooling thepart followed by removing any excess silicon exuded out of the part, andmachining the part to final tolerances such as by diamond grinding. Thesurface of the part can be sealed with a CVD SiC coating of any suitablethickness such as 50 to 500 μm, preferably around 200 μm for parts notdirectly exposed to the plasma or the coating can be in excess of 1 mm,preferably 2 mm or more for parts exposed directly to the plasma.

The slip cast part can be used in any plasma reaction chamber wherein itis desired to reduce particle contamination and/or reduce process drift.An example of a single wafer vacuum processing chamber 2 having aninductively coupled plasma source is shown in FIG. 1 wherein processinggas is supplied to the processing chamber 2 by suitable apparatus (notshown) such as gas distribution rings, gas distribution plate, injectionnozzles, etc., and a vacuum is maintained in the interior 4 of thechamber by suitable vacuum pump apparatus. The substrate to be processedin the chamber can comprise a silicon semiconductor wafer 6 supported ona substrate support 8. The substrate support 8 can include anelectrostatic chuck and a focus ring 10. The vacuum pump can beconnected to a large outlet port 12 in an endwall such as the bottom ofprocess chamber. The vacuum processing chamber can include a dielectricwindow 14, a gas distribution plate 16 and RF power can be supplied tothe chamber through an external RF antenna such as a planar coil 18outside the dielectric window 14 on an endwall such as the top of thechamber. However, the plasma generating source can be of any other typeof plasma generating equipment such as that of an ECR reactor, acapacitively coupled parallel plate reactor, a surface wave reactor, amagnetron reactor, helicon reactor, helical resonator, etc. The plasmagenerating source can be attached to a modular mounting arrangement suchas an annular mounting flange which is removably mounted on the endwallof the chamber.

In order to maintain a vacuum tight seal between the mounting flange andthe chamber 2, suitable O-ring seals can be fitted within grooves in theendwall of the chamber 2 and RF shielding members can surround thevacuum seals. If a large vacuum force is provided by the vacuum pump, itis not necessary to utilize fasteners for attaching the mounting flangeto the chamber 2. Instead, the mounting flange can simply rest on theendwall of the chamber 2. If desired, the mounting flange or anotherpart of the plasma generating source assembly can be hinged to thechamber 2 such that the plasma generating source can be pivoted to anorientation such as a vertical orientation for servicing the interior 4of the chamber 2.

The chamber includes a liner 20, a plasma screen 22 for confining theplasma in the space surrounding the wafer 6 extends inwardly from thelower end of the liner 20 and a wafer passage insert 21. The liner 20can be supported in any suitable way such as by an elastically bendableframe in the case of a solid cylindrical liner which includes an innersupport frame 24 and an outer support frame 26. In order to maintain theliner at a desired temperature during processing of a substrate, aheater 28 can be provided on the top of the inner frame support 24. Inoperation, the heater 28 is effective to heat the liner 20 and removalof heat from the liner 20 can be accomplished by a temperaturecontrolled member 30 which withdraws heat from the liner through theinner and outer frames. Other types of heating arrangements such as aheater embedded in the liner or suitable radiant heating arrangementscan also be used.

As shown in FIG. 2, the chamber can have a modular design which allowsvarious plasma generating sources to be mounted thereon. Further, thesubstrate support 8 can be supported at one end of a support arm mountedin a cantilever fashion such that the entire substrate support/supportarm assembly can be removed from the chamber by passing the assemblythrough an opening 32 in the sidewall of the chamber. The chamber can beof any suitable material and according to a preferred embodiment of theinvention the chamber is formed out of a single piece of aluminum or analuminum alloy.

According to a first embodiment of the invention, the plasma chamberliner 20 comprises interlocking ceramic liner elements such as flattiles 34, as shown in FIGS. 3 and 4. To provide an electrical groundpath for the plasma, the tiles 34 are preferably of an electricallyconductive material such as silicon and carbon. For example, the tilescan be entirely of CVD SiC or Si impregnated SiC coated with CVD SiC.Such a material provides an added benefit in that it does not containaluminum and thus reduces Al contamination of processed substrates. TheSiC tiles can be bonded to an aluminum backing plate 36 using anelectrically conductive elastomer 38 which can absorb lateral stressescaused by different thermal expansion coefficients of the SiC and Al.Each tile and backing plate assembly can be attached directly orindirectly to the chamber wall. For example, the tiles can be supportedby a support frame 40 which includes an inner frame 42 and an outerframe 44. Temperature control of the liner can be achieved by a heater48 supplied power by electrical leads 49 and a temperature controlledmember 50.

The elastomeric joint can comprise any suitable elastomeric materialsuch as a polymer material compatible with a vacuum environment andresistant to thermal degradation at high temperatures such as above 200°C. The elastomer material can optionally include a filler ofelectrically and/or thermally conductive particles or other shapedfiller such as wire mesh, woven or non-woven conductive fabric, etc.Polymeric materials which can be used in plasma environments above 160°C. include polyimide, polyketone, polyetherketone, polyether sulfone,polyethylene terephthalate, fluoroethylene propylene copolymers,cellulose, triacetates, silicone, and rubber. Examples of high purityelastomeric materials include one-component room temperature curingadhesives available from General Electric as RTV 133 and RTV 167, aone-component flowable heat-curable (e.g. over 100° C.) adhesiveavailable from General Electric as TSE 3221, and a two-part additioncure elastomer available from Dow Corning as “SILASTIC.” An especiallypreferred elastomer is a polydimethylsiloxane containing elastomer suchas a catalyst cured, e.g. Pt-cured, elastomer available from Rhodia asV217, an elastomer stable at temperatures of 250° C. and higher.

In the case where the elastomer is an electrically conductive elastomer,the electrically conductive filler material can comprise particles of aan electrically conductive metal or metal alloy. A preferred metal foruse in the impurity sensitive environment of a plasma reaction chamberis an aluminum alloy such as a 5-20 weight % silicon containing aluminumbase alloy. For example, the aluminum alloy can include about 15 wt %silicon. However, filler particles of silicon or silicon carbide canalso be used.

A plasma screen 52 extends inwardly from a lower edge of the tiles 34.The plasma screen 52 is preferably of an electrically conductive ceramicmaterial such as Si impregnated SiC coated with CVD SiC and includesopenings 54 which are small enough to confine the plasma but allowprocess gas and processing byproducts to be removed by the vacuum pump.

The heater 48 can comprise an electrical resistance heating, elementembedded in an aluminum casting. Thus, by passing electrical currentthrough the heating element, heat will be supplied to the aluminumcasting which in turn conducts heat into the inner frame 42, thealuminum backing plates 36, the heat conductive elastomer 38 and intothe tiles 34. During heating and cooling of the aluminum body of theheater, the heater will expand to a greater extent than the ceramicliner formed by the tiles 34. In order to accommodate such expansion andcontraction, the inner and outer support frames are configured to beelastically bendable. For example, the frames can be segmented such thata series of axially extending lower portions thereof are separated byaxially extending slits. In addition, the inner and outer frames can beconfigured to provide a desired amount of thermal conductance. Forinstance, the outer frame 44 can be of a metal such as aluminum or analuminum alloy and a lower portion thereof can have a thicknesssufficient to withdraw heat from the liner and a thin upper portion toallow adequate bending of the outer frame due to thermal stresses duringprocessing of a semiconductor substrate.

FIG. 5 shows a portion of the chamber wall wherein a substrate such as awafer can be introduced and removed from the chamber through a transportslot 55 in a wafer passage insert. In the arrangement shown in FIG. 5,some of the tiles 34 are shorter in the axial direction in the vicinityof the slot 55. The slot 55 is preferably formed from an integral pieceof Si impregnated SiC coated with CVD SiC.

In order to prevent a line of sight between the wafer 6 and the chamberwall 46, each tile 34 can have edges 56 which interlock with matingedges of adjacent tiles, as shown in FIG. 6. As shown in thisalternative embodiment, the chamber 58 can have polygonal inner surfaces60 wherein the tiles are bonded directly to flat surfaces 60 of thechamber by an electrically and thermally conductive elastomer. Such anarrangement is advantageous in that it has fewer parts than thetile/backing plate arrangement and allows liner removal for cleaning andreplacement to be carried out more quickly.

FIG. 7 shows a perspective view of a slip cast wafer passage insert 70.The insert 70 includes an inner surface 72 forming the wafer transferslot 55 shown in FIG. 5. The shape of the part shown in FIG. 7 can beslip cast in the manner described above and the inner surface 72 andoptionally the entire outer surface 74 can be coated with CVD SiC. Theside of the insert facing the interior of the plasma chamber includesrectilinear edges 76 which abut surfaces of the tiles 34 opposite to theside of the tiles facing the interior of the chamber. FIG. 8 shows a topview of the insert 70 and FIG. 9 is an enlarged view of a corner 78 ofone of the edges 76, the edge 78 including an angled section 79 having alength corresponding to the wall thickness of insert 70.

In the foregoing embodiments, the plasma in the chamber can be confinedby the SiC surfaces of the gas distribution plate, the liner, the plasmascreen and the substrate support which extends upwardly through theinner periphery of the plasma screen. Because the CVD coating on the Siimpregnated SiC parts are located between the plasma and aluminumsurfaces of the chamber, sputtering of the Al surfaces by the plasma isminimized and contaminating processed wafers with Al is reduced comparedto chambers having Al surfaces with line-of-sight to the processedwafer.

In the foregoing embodiment, the liner comprises tiles of Si impregnatedSiC coated with CVD SiC bonded to an aluminum backing plate by anelectrically and/or thermally conductive elastomer bonding material. Ifdesired, the liner can comprise a continuous surface rather than theindividual tiles. The chamber wall can be of any desired configurationsuch as cylindrical, polygonal, etc. A suitable access opening in thewafer passage insert allows passage of individual wafers into and out ofthe chamber and additional openings can be provided in Si impregnatedSiC parts coated with CVD SiC to allow various measurements to be madeby conventional accessories such as process monitoring equipment. Thetiles can have a flat rectangular surface facing the interior of thechamber. Alternatively, the exposed surface of the tiles can be curvedsuch that the tiles form a cylindrical inner wall of the chamber.

In the embodiment wherein the tile and backing plate assemblies arebolted to an Al inner support frame which extends around the inner wallof the chamber, the thermal stresses generated during start-up,operation and shut-down of the plasma chamber can be accommodated. Thenumber of SiC tiles can be chosen to achieve a desired limit on partand/or bond stresses generated due to thermal forces encountered in theplasma chamber.

In the embodiment wherein a lower flange of the inner support frame isbolted to the lower edge of an Al outer support frame and a flange atthe upper edge of the outer support frame is bolted to a top platelocated on top of the chamber, the outer support is segmented intovertically extending plates separated by slots which extend from thelower end of the outer support frame to the top flange. In order toprovide temperature control of the SiC tiled surface, a heater locatedabove the top flange of the inner support frame can be bolted to theinner frame. With such an arrangement, the heater can generate heatwhich is thermally conducted from the inner support frame to the backingplate and SiC tile. The heater can comprise a single resistance heaterwhich extends entirely around the inner wall of the chamber.Alternatively, the heater can comprise any suitable heater arrangementwhich achieves the desired temperature control of the liner, e.g.,maintaining the inner surface of the liner at a desired temperature suchas in the range of 80 to 160° C. during plasma etching of dielectricmaterials such as silicon oxide.

The chamber can include a plasma screen surrounding the substratesupport. The annular screen can be attached to a carrier ring by anysuitable technique. For instance, the screen can be adhesively bonded tothe carrier ring by the elastomer bonding material discussed earlier. Inaddition, the carrier ring can be bolted to a lower flange on the innerframe such that the screen is clamped between the carrier ring and theflange. The screen can be of any suitable material which will withstanda plasma environment for semiconductor production. Silicon carbide is apreferred material for the screen. The screen can comprise a singleunitary ring or a plurality of spaced apart ring segments. For instance,the screen can include circumferentially spaced apart segments.

In order to accommodate the wafer passage insert, the inner and outerframes include cut-outs therein and the tiles surrounding wafer transferthe slot are arranged such that smaller tiles are below the slot andlarger tiles are above the slot. The wafer passage insert preferablycomprises a single piece of slip cast SiC which is impregnated with Siand then coated with CVD SiC. If desired, the insert can be made from anassembly of several pieces of such material.

According to the embodiment of the invention wherein line-of-sightsurfaces of aluminum components are avoided by covering the surfaceswith the SiC tiles, the edges of the tiles are preferably designed suchthat they overlap each other. For instance, the tiles can have matingedges wherein a projection on one tile is received in a recess in anadjacent tile. This effect can be obtained by any edge design wherein arectilinear path is not provided between the opposed surfaces of thetile. Thus, a mating curved or multi-sided edge surface such as aV-shaped, U-shaped, W-shaped, groove-shaped, notch-shaped,offset-shaped, etc. type edge can provide the desired mating tile edge.

The interlocking tile joints eliminate line-of-sight to aluminumcomponents and accommodate differential thermal expansion/contraction ofliner components during startup, operation and/or shutdown of the plasmareactor. For instance, heat from the heater and/or plasma ion thermalenergy deposited on the tiles is thermally conducted by the inner frame,through the elastomer bond, up the outer frame and into the chamber topplate. Due to water cooling of the top plate via cooling channels, theheat transferred through outer frame is removed from the chamber.

During processing of semiconductor substrates, the tiles can bepreheated by the heater before plasma is generated in the chamber. Forinstance, the tiles can be heated to a desired temperature by the heaterand a thermal control system can be used to adjust the heater power tomaintain the tiles at the desired temperature. After plasma is generatedin the chamber, the control system can automatically reduce the heaterpower to maintain the desired time temperature. Further, the thermalimpedances of the inner and/or outer frames can be adjusted to achievethe desired range of tile operating temperatures and limit the heatermaximum temperature.

During processing of semiconductor substrates such as plasma etching ofsilicon wafers, in order to minimize deposition of polymer from gaseousbyproducts produced during the etching process, it is desirable tomaintain chamber surfaces exposed to the plasma at temperatures of about80° C. to about 160° C., preferably 110 to 150° C. In addition, suchtemperature control of these surfaces provides reduction in processingdrift during sequential processing of individual wafers. Prior tostriking a plasma in the chamber, a resistance heater can be used toheat the ceramic liner by thermal conduction, i.e., heat from the heaterpasses through a resilient Al frame to the ceramic liner. In such anarrangement, the heater and part of the Al frame in contact therewithmay heat to around 300° C. in order to heat the ceramic liner to around150° C. The resilient Al frame comprised of the inner and outer framesallows the part of the Al frame in contact with the heater to expandrelative to the portion of the Al frame in contact with the ceramicliner and thus accommodate any bending stresses on the intermediate partof the Al frame.

If desired, one or more parts of the chamber can be made of CVD SiC. TheCVD SiC can be deposited on a substrate such as graphite and grown to adesired thickness after which the substrate is removed such as bymachining. For example, in the case of a cylindrical liner, CVD SiC canbe deposited to a desired thickness on a graphite cylinder and thegraphite cylinder is later machined away leaving the CVD SiC cylinderliner. Advantages of the CVD SiC include high thermal conductivity(e.g., CVD SiC has about twice as much thermal conductivity as sinteredSiC) and tailored electrical resistivity (e.g., resistivity of SiC canbe varied from electrically conducting to semiconducting). An advantageof using CVD SiC for the reactor components is that it is possible toobtain a highly uniform temperature distribution across the surface ofthe component inside the reactor. In the case of processing wherein thecomponent is maintained at a high enough temperature to minimize polymerbuildup on the exposed surfaces of the component, the use of CVD SiC ishighly advantageous from the standpoint of temperature control andminimizing particle generation.

An example of preparing a slip cast component in accordance with theinvention is as follows.

A mixture of 1 part by weight of medium particles of SiC powder withaverage particle diameters between 10 μm and 30 μm and 1-2.5 parts byweight of coarse particles of SiC powder with average particle diametersbetween 80 μm and 200 μm is kneaded and granulated after adding anorganic binding agent. Then, the mixture is formed into a shape definedby a plaster mold after which the shaped part is dried. Next, the shapedpart is presintered at 800 to 1200° C. followed by reaction sintering at1500 to 1800° C. while impregnating the shaped part with Si. Thesintered part is then placed in a vacuum furnace and coated with SiCusing a mixture of trichloromethyl silane gas at 4 ml/min with hydrogenas a carrier gas at 4000 ml/min. As a result, a slip cast SiC part isproduced with a CVD SiC coating.

The foregoing has described the principles, preferred embodiments andmodes of operation of the present invention. However, the inventionshould not be construed as being limited to the particular embodimentsdiscussed. Thus, the above-described embodiments should be regarded asillustrative rather than restrictive, and it should be appreciated thatvariations may be made in those embodiments by workers skilled in theart without departing from the scope of the present invention as definedby the following claims.

1. A method of processing semiconductor substrates and reducing particlecontamination and/or process drift during consecutive processing of thesubstrates, the method comprising steps of: (a) placing a substrate on asubstrate holder in an interior space of a plasma processing chamber,the processing chamber including at least one slip cast part having asurface exposed to the interior space, the slip cast part having freesilicon contained therein and a protective layer on the surface whichprotects the silicon from being attacked by the plasma in the interiorspace; (b) processing the substrate by supplying process gas to theprocessing chamber and energizing the process gas into a plasma state inthe processing chamber, the slip cast part being exposed to the plasmaand optionally providing a ground path for RF current sustaining theplasma; (c) removing the substrate from the processing chamber; and (d)consecutively processing additional substrates in the processing chamberby repeating steps (a-c) while minimizing particle contamination of thesubstrates and/or reducing process drift during the processing step as aresult of protecting the free silicon from attack by the plasma.
 2. Themethod according to claim 1, wherein the slip cast part comprises aliner within a sidewall of the processing chamber, the processingchamber including a substantially planar antenna which energizes theprocess gas into the plasma state by supplying RF power to the antennaand the process gas comprising one or more hydrofluorocarbon gases. 3.The method according to claim 1, wherein the plasma comprises a highdensity plasma and the substrates are processed by etching an oxidelayer on the substrates with the high density plasma while supplying anRF bias to the substrates.
 4. The method according to claim 1, whereinthe slip cast part comprises a liner within a sidewall of the processingchamber, a gas distribution plate supplying the process gas to theprocessing chamber, a perforated baffle extending between the substrateholder and an inner wail of the processing chamber, a wafer passageinsert and/or a focus ring surrounding the substrate.
 5. The methodaccording to claim 1, wherein the slip cast part comprises a waferpassage insert fitted in an opening in a ceramic liner within a sidewallof the processing chamber, the liner being heated by a heater whichmaintains the liner at a desired temperature.
 6. The method according toclaim 1, wherein the slip cast part consists essentially of siliconimpregnated slip cast SiC coated with CVD SiC.
 7. The method accordingto claim 1, wherein the slip cast part comprises a heated liner and abaffle, the liner surrounding the substrate holder and the bafflecomprising a foraniinous ring extending between the liner and thesubstrate holder, the liner being heated to a temperature above roomtemperature during the processing step.
 8. The method according to claim1, wherein the slip cast part comprises a gas distribution plate havinga resistivity high enough to allow RF energy to pass therethrough, theprocess gas being energized by an antenna which couples RF energy intothe chamber through the gas distribution plate.
 9. The method accordingto claim 8, wherein the slip cast part further comprises a chamber linerhaving a resistivity below 200 Ω·cm.